Furnace and afterburner



Elite States utcnt 2,752,870 7/1956 Short ct 2,845,882

[72] Inventor Samuel Foresto 243 Willis Ave., Mineola, New York 115018/1 58 Brattonuu...

S m T. H N 1 H 1 m mm A mm P N a mmmm E mmm CrUC 0 038 666 999 NH 022508 6007 644 040 69 8 %0 AM 22 .6 t I 9 58 7S0 0. d w. m d P e mm AFP.11] I25 224 [[1 FURNACE AND AFTERBURNER 5 Claims, 2 Drawing Figs.

Primary Examiner-Edward G. Favors Auorney-1erome Bauer ll0/8(A): 122/4,7(C&D) 521x); 23/277 [51] [50] 1 Field g the residue found in e gaseousphase of burned fuel comprising a high temperature body heated by anelectrical] ABSTRACT: Apparatus for consumin y resistant coil wrappedource of power.

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D E W N U M U 122/52 about the body and connected to a s Patented Oct.6, 1970 1 INVENTOR. SAMUEL FORESTO M ATTORNEY m FURNACE AND AIFTERBURNERBACKGROUND OF THE INVENTION The present invention relates toimprovements in heating systems and, in particular, to an improved afterburner for furnaces, ovens or other devices employing coal, oil, gas orthe like, as the heating medium.

As is well known, the combustion of such fuels as listed above is rarelycomplete and there is nearly always considerable residue of particulatematter, fly ash and unburned fuel expelled to the atmosphere. Thisunburned fuel, fly ash, etc. is often noxious and harmful to health, aswell as being of considerable nuisance as dirt.

Additionally, the accumulation of unburned fuel within the furnace inthe form of soot severely affects, over a period of time, the efficiencyof subsequent combustion and the heat exchange effects of the furnace oroven.

SUMMARY OF THE INVENTION It is the purpose of this invention to providea novel afterburner for completing the combustion of fuels and,consequently, reducing to a most negligible amount the deleteriousemission of toxic, noxious and harmful materials.

It is further an object of this invention to provide afterburner meansfor increasing the combustion efficiency of fuels as well as the heatexchange characteristics of furnaces and ovens.

It has been particularly found that the gaseous phase of combustioncontains minute particles of fuel, ash, minerals or other impuritieswhich do not burn at the normal temperature levels of the fuels, butare, in fact, consumed only at tempera tures far higher than initialcombustion. Accordingly, it is also an object of this invention toprovide afterburner means for increasing the temperature of the gaseousphase of combustion.

Briefly, the present invention provides an independently controlledelectrically heated afterburner system adapted to be inserted withinthat part of an oven or furnace wherein the gaseous omissions ofcombustion are passed. This independent heating system increases thetemperature of the gaseous phase to such a degree as to completelyconsume any residue contained therein.

The present device further enables modification to be made to thefurnace or oven to produce greater heat exchange efficiency. With thismechanism the normal conduction of smoke or heated air, i.e., thegaseous phase need not be passed almost directly out of the furnace intothe chimney, but because of its cleaner nature and hotter temperature itcan be circulated more fully in the furnace so as to extract the heattherefrom in increased exchange effect.

BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages, aswell as others, will be apparent from the following description whereinreference is made to the accompanying description in which:

FIG. I is a cross-sectional perspective view of a furnace employing oneembodiment of a device made in accordance with the present invention,and

FIG. 2 is a cross-sectional view of a chimney flue showing another formof the present invention.

In FIG. 1, the general details of an oil or gas furnace is shown. Itwill be appreciated that such type of furnace is shown for its exemplaryvalue and should not be taken to limit the application of the presentinvention. The furnace, of course, can be an incinerator, oven or aninternal combustion engine.

The furnace IOcomprises an outer shell or cast iron casing 12 having agenerally hollow interior in which is located a boiler heat exchangesection 14 containing the media to be heated. Through the boiler 14 runsa plurality of open, generally parallel tubes 16 communicating at oneend with a large open combustion chamber or fire box 18. The other endof tubes 16 communicate with a tortuous passage or second chamber 20substantially surrounding the boiler 14 to which a chimney flue 22 isconnected. It will be observed that the tubes 16 are not in directcommunication with the chimney flue 22 which is also below the level oftubes 16 and that the passage 20 virtually surrounds the boiler 14. Thisis different from the standard prior construction of furnaces whichgenerally have their chimney flues directly above the end of the tubes16 so as to exhaust the gas and smoke almost immediately after itspassage through the boiler. The advantages of the present novelconstruction will be enlarged upon in detail later.

Returning to FIG. 1, the construction of the furnace is generallycompleted by the insertion of a burner 24 into the fire box 18. Fuelline control systems, as well as access doors, are not here shown asthey are well known and their addition serving little purpose to theexposition of the present invention is omitted for the sake of brevity.

Thus, except for the construction of the enveloping passage 20, therehas been described a standard conventional furnace which when operatedproduces within the burner 24 a fire. The fire extends into thecombustion chamber 18 as indicated by the heavy arrows F emittingintertwined heat radiation and convection and conduction currentsexhausting its fumes, smoke, etc. through the furnace as indicated bythe lighter arrows S. The heat rises together with the smoke through thecombustion chamber into the tubes 16, heating the media in boiler 14and, subsequently, passing out of chimney flue 22.

In the prior art devices, the heated gases, smoke, etc. would normallycontain huge amounts of unburned particles, soot, etc. which would firstdeposit in the combustion chamber and, subsequently, the tubes and thenexhaust into the atmosphere. The efficiency of the furnace is therebyconstantly diminished and the air polluted with noxious and toxicmaterial.

According to the present invention, the unburned gases, etc. areconsumed and treated by the insertion within the exit portion of thecombustion chamber 18 of an independent heating unit or afterburnerapparatus generally indicated by the arrow 26. This heating unitcomprises a high heat resistant ceramic body 28 about which is wrapped aheating coil 30 connected to a suitable source of electricity such as abattery or house current (not shown in FIG. 1). Suitable switch meansfor activating the coil 30 and for variably controlling its temperaturemay also be employed although not shown in FIG. 1. Such switches andcontrols are shown in connection with the form described later inconnection with FIG. 2.

The ceramic body 28 is shaped or contoured in flaring or enlargingfashion and is located in the passage directly connecting the fire box18 with the heat exchange section 14. This results in providing a largersurface of the body 28, in that exit portion of the fire box 18 that isremote from or upstream of the heat exchanger section 14. It is notedthat the exit portion of the passage is thus restricted by the unit 26that substantially fills the passage. The coil 30 may be made of anyhigh resistance wire. Nichrome, an alloy of nickel and chromium, hasbeen found suitable. The coil 30 may also be wrapped in any suitablemanner about the ceramic body 28 to effect the degree of heat andtemperature desired. The body 28 may, if desired, be provided with holesor openings 32 to facilitate passage of gas or smoke through the heatingunit 26 and the heating unit 26 is itself spaced from the walls of thecombustion chamber or furnace so as to permit passage of airtherearound.

In operation, the afterburner 26 is activated so that its coil 30assumes a temperature which by its own nature is far in excess than thecombustion temperature of the fuel in the burner 24. The heat of thecoil 30 is transmitted directly to the ceramic body 28 raising itstemperature far in excess of the temperature of fuel combustion. It willbe observed that no matter how the coil 30 is wrapped, the upper edgesof the heat resistant ceramic body 28 become hotter than the loweredges. This occurs because heat tends to rise. Therefore, upon themovement of the exhaust smoke and heated gas from the fire box 18 on itsway into the tubes 16, the particles of dirt, fly ash, vapor andunburned fuel contained in the moving gas coming into contact with thehotter body 28, are heated to such a degree that virtually all suchresidue is immediately ignited and consumed. Consequently, the heatedgas leaving the unit 26 is not only cleaned and freed of pollutants butit is cleansed prior to its entry into the heat exchanger tubes 16.

As a result of the use of the present device 26, within the furnace,greater heat exchange efficiency in the boiler is immediately possible.Thus, more efficient heat exchange is obtained over substantially longerperiods of time because the tubes remain free and clean of insulatingparticles that normally accumulate and deposit on them. The life of thefurnace, i.e., before it requires cleaning, is significantly longer.Because of the total consumption of pollutants by the device 26, thedeposition of soot or caked dirt within the furnace and in particularwithin the tubes is markedly reduced. Moreover, the smoke exhausted fromthe furnace is free of pollutants and its harmful constituents,contributing to a cleaner atmosphere.

The beneficial results obtained with the present device 26 now enableseven the furnace itself to be modified to obtain even greaterefficiencies. The exhausted gas, of course, is hotter than the airproduced in the combustion chamber therefore it may be utilized over alonger period in heat exchange relationship with the boiler. Thus, theexit passage from boiler to flue 22 may be enlarged so that the heatedair circulates about the boiler 18 in contact with its outer surface.Consequently, the medium contained in the boiler is heated not only fromthe inside, through tubes 16, but from the outside. This constructionhas been found not to decrease or adversely effect the draft" within thefurnace and, in fact, the draft is most often assisted to provide a moreefficient flow so that the chimney flue exit may be located anywhere.

In prior art furnaces the flue was located above and to the rear of theboiler (indicated by the dotted lines). This is no longer necessary inthe present invention. The exhaust flue 22 now may be located in anyconvenient position even at the front of the furnace as shown. This ispossible because the exhaust gas is cleaned of all pollutants during itsmovement through the furnace and, therefore, the prior art need for astrong draft to remove and lift the pollutants out of the furnace intothe atmosphere by locating the flue at the hottest point of the furnaceis obviated. By locating the flue 22 at a lower point, as shown, the hotclean gas applies its heat longer to the heat exchanger 14 therebyresulting in a more efficient use of the exhaust gas over a longerperiod.

Having thus described one form of the invention, its mode of operationand its advantages, it will be appreciated that various changes andadaption can be made. For example, the flaring contour of theafterburner 26 may be made to take any shape and it may be located atany position in the furnace l4 and associated structure. The device 26may be employed in any type furnace not only that having a supplied fuelsuch as gas or oil but one having an indigenous fuel as an incineratoror waste burner. Internal combustion units may also be fitted with thepresent device. The device is not expensive to operate since electricityis cheap and plentiful and the amount used need not be too great.

The present device may be used also to dispose of the pollutant in thegas exhausted into the atmosphere. This application is shown in FIG. 2wherein the device 26a comprises a conical high heat resistant ceramicbody 34 about which is wrapped a heating coil 36. The conical body 34 issupported within a cylindrical flue 36 of a chimney 38 by brackets 40.The direction of air flow is indicated by arrows T. The body 34 may beprovided with holes or openings 42 to facilitate passage of air throughthe chimney and to also increase its effective heated surface.

It will be clearly observed in FIG. 2 that the total volume of air isforced almost completely into contact with the surface of the body 34,which will, of course, be hotter at its upper end. Since the device 260is located in the chimney flue 38, ignition and consumption of thepollutants carried in the flue gas results prior to the discharge of theflue gas into the at mosphere. As the flue gas rises in the chimney 38,it strikes and impinges upon the far hotter surface of the body 34.Because heat rises, the upper wider portion of the conical body 34 ishotter in comparison to the lower narrower apex portion of the same bodythat is directed toward the upstream of the gas. In consequence, thosepollutants that strike the surface of the body 34 and which ignite atlow temperatures will combust completely immediately upon contact withthe narrower portion of the body 34. However, those pollutants carriedby the gas that ignite under higher temperatures will travel upwardalong the surface of the body 34 and during their movement they willcome into contact with the hotter portions of the surface of the bodyand, thus, will ignite also. Hence, the pollutants in the gas rising inthe chimney 38 will be ignited and consumed thereby removing them fromthe gas that exits into the atmosphere.

The openings 42 provided in the body 34 serve to increase the effectivesurface area of the body and, thus, cause the gas to follow a tortuouspath during which the gas is so heated that pollutants moving with thegas must come into contact with some surface portion of the device tothereby assure the ignition and combustion of the pollutants to removethem from the flowing gas. The holes 42 further increase the effectiveopening between the device 26a and the surrounding surface of thechimney 38 so that the movement of the gas through the chimney is notslowed. Rather, the construction of the body 34 assures that the gas isattracted and its pollutants carried thereby strike and impinge upon thebody 34 to complete their combustion prior to their exhaust into theatmosphere.

In FIG. 2, the source of current 44 and the variable temperaturecontrols 46 and switch 48 are shown conventionally connected to operatein the conventional manner.

In the aforedescribed embodiments and uses of the afterburner devices 26and 26a, the means to initially heat and retain such devices attemperatures in excess of the unburned matter or pollutants contained inthe gaseous phase of the burned fuel were described as electricallyoperated. Such description was to enable an understanding of thesimplicity of the purpose of the invention. Those skilled in the artwill readily recognize that the devices 26 and 260 may be raised to thedesired operating temperatures in excess of the combustion temperaturesof the pollutants by heating the same with gas or oil fired elements.This is especially true in the embodiment of FIG. 1 where some of theoil fired heat of the burner 24 may be diverted to heat the device 26 toits desired temperature to fully consume what unburned matter or otherpollutants remain in the gaseous phase of the burned fuel.

It will be observed that the term afterburner when used in thisspecification refers to an independent heating device employed bothwithin the furnace and in the exhaust portion or chimney of an oven orengine. It is intended to broadly define a device located in flowrelationship with the gas phase so as to consume the residue left afterthe initial burning of fuel.

It will thus be appreciated that the objectives and advantages of thepresent invention are simply obtained and while described herein astaking some definite form is adaptable to various modifications andchanges. It is thus intended that the invention be limited only by theappended claims.

I claim:

1. A furnace comprising:

a casing;

heat exchange means located within said casing and defining therewith afirst chamber for the combustion of fuel and a second chamber at leastin part surrounding the outer surface of said heat exchange means;

said heat exchange means having an inner surface in connection with eachof said first and second chambers thereby permitting heat to pass incontact with said heat exchanger from one surface to said other;

said second chamber being in communication with exhaust means to exhaustgas from said furnace; and

an afterburner located in gas flow relationship between saidfirstchamber and said heat exchanger to increase the temperature of thegaseous phase of the burned fuel to consume residue matter therein priorto contact with said inner surface of said heat exchange means wherebyheated gas free of residue passes in contact with each of the surfacesof said heat exchanger prior to passage through the exhaust means.

2. The furnace according to claim 1 wherein said heat exchange meanscomprises a boiler having a plurality of hollow tubes located therein,each communicating with both the first and second chambers of saidfurnace.

3. The furnace according to claim 1 wherein said exhaust means islocated at the farthest extreme in gas flow relationnected with saidcoil for controlling the temperature of said coil.

